In order to improve the transport capacity of an elevator system with small demand on space two elevator cars are arranged in the same elevator shaft. The two elevator cars are movable independently of one another along a common guide path usable by both.
Such elevator systems with two or optionally more than two elevator cars in the same elevator shaft are primarily provided for high buildings. The merits of these double car elevators are relevant particularly when the individual elevator cars can circulate at a comparatively high speed.
Even in conventional elevator systems with only one elevator car, in the case of elevator systems of that kind with several elevator cars tensioning devices with lower cables are provided when travel speeds above a certain limit speed, for example above approximately 2.5 m/s are envisaged. The tensioning device for the lower cables preferably acts in a blocking manner in order to prevent the counterweight from jumping when the car safety brakes come into action, for which purpose the counterweight is retarded by a reaction force introduced into the elevator shaft.
Due to the vertically fluctuating arrangement of two elevator cars it is difficult to accommodate drive elements, supporting elements and traction elements in the form of flexible flat belts and/or cables as well as roller arrangements for drive, guidance and deflection of the supporting elements and traction elements in the common elevator shaft. As further flexible elements the lower cables must also be arranged together with the rollers required for the deflection and guidance thereof. A further requirement is to realize a suitable introduction of the forces into the elevator cars.
WO 2006/065241 discloses an elevator system of that kind with two elevator cars which can be moved independently of one another along a travel path able to be utilized by both elevator cars. The two elevator cars are suspended at individual supporting and traction means and have individual counterweights. The upper elevator car has a central 1:1 suspension and the lower elevator car has a symmetrical 1:2 suspension and deflecting rollers for guidance or directing the supporting and traction means. A satisfactory solution for the mounting, deflecting and guidance of lower cable arrangements is not described.